1. Field of the Invention
This invention relates generally to a method and an apparatus capable of deploying and subsequently supporting a lightweight space structure such as a solar array, reflector, sunshield, radar array, antenna, or concentrator. The invention relates more specifically to a method and lightweight apparatus that provide for the controlled deployment of an inflatable shell containing a space frame assembly, and the subsequent rigidization of the assembly so as to support the space structure.
2. Description of Related Art
Most conventional methods for deploying and supporting a space structure accomplish the deployment by means of deployable truss structures consisting of relatively heavy elements such as rigid members, hinges, latches, and cables. Increases in the number of satellites to be launched over the next several decades, however, will emphasize the need for the reduction of space hardware mass, stowage volume, and cost.
One approach to realizing these reductions is through the use of inflatable, deployable, space structures. Inflatable structures offer many benefits over conventional deployable structures because they are lower in mass and can be packaged into small volumes, which reduces launch vehicle size and cost. The performance benefit margin of inflatable structures increases as the size of the structure increases, thus making the technology more attractive for large-scale systems. Examples of satellite components that benefit from the utilization of inflatable structures include solar arrays, communications antennas, radar antennas, thermal/light shields, and solar sails.
Although inflatable tubular structures weigh less than deployable truss structures consisting of elements such as rigid members, hinges, latches, and cables, the weight of the inflatable tubular structures is not insignificant.
Therefore, a need exists for a method and an apparatus capable of facilitating the deployment, and subsequent support, of a space structure, but which can do so with an overall apparatus weight which is less than that of conventional inflatable deployment structures.
It is an object of the present invention to provide a method and an apparatus capable of deploying and subsequently supporting a space structure. It is a further object of the present invention to provide a method and an apparatus capable of facilitating the deployment by controlling both the rate and the directionality of deployment. It is a still further object of the present invention to provide a method and an apparatus capable of facilitating the deployment, and subsequent support, of the space structure, but which can do so with an overall apparatus weight which is less than that of conventional inflatable deployment structures.
Accordingly, the present invention is directed to a deployable space frame comprising a packageable, deployable, and rigidizable frame assembly; a packageable, deployable, and inflatable frame assembly shell disposed around the frame assembly; means for attaching the frame assembly shell to the fame assembly; and a shell inflator.
The present invention is also directed to a method of packaging and deploying the space frame. The method comprises (a) collapsing the frame assembly by packaging the shell to provide a packaged frame assembly/shell; (b) controllably deploying the frame assembly and the shell from the packaged frame assembly/shell by employing the shell inflator to inflate the shell while imparting a resistance to the shell to resist deployment such that the internal gas pressure required to continue deployment is sufficient to fully inflate that portion of the shell to which gas has been introduced; (c) continuing to resist deployment until the frame assembly and the shell are deployed; (d) terminating the introduction of gas into the shell; (e) rigidizing the frame assembly; and (f) depressurizing the shell.
Thus, as the shell inflates, it deploys both the shell and the frame assembly contained therein in a controlled manner. Once the deployed shell is fully inflated, the frame assembly is rigidized to provide the support for the space structure. The shell is then depressurized and assumes an essentially passive role, apart from providing environmental protection for the rigidized frame assembly.
The advantages associated with the present invention are numerous. First, as indicated above, most conventional methods for deploying and supporting a space structure accomplish these tasks by means of either deployable truss structures consisting of relatively heavy elements, or inflatable structures. The space frame, however, requires substantially less material to accomplish the same structural performance as conventional inflatable structures, and is therefore lower in mass. The present invention, therefore, provides a lightweight means for both deploying and supporting a variety of space structures. Furthermore, by virtue of its inflatable means for deployment and rigidizable means for support, the invention comprises a lighter-weight system with fewer moving parts, thereby providing a higher degree of system reliability. Finally, the ability to collapse the structure for launch results in a packed volume which is minimal when compared with the aforementioned conventional structures.
Thus, while specifically facilitating as its primary application the deployment of lightweight space structures, the invention also more generally provides for the deployment of any lightweight structure that can then be maintained in place by the rigidity of the frame assembly.